Treatment of articular cartilage defects is typically accomplished by the microfracture procedure. This procedure is performed arthroscopically. Although articular cartilage defects may occur in any joint, the microfracture procedure is typically performed in the knee or shoulder. The surgeon visually assesses the defect and performs the procedure using special instruments that are inserted through small incisions around the joint. Unstable and loose cartilage is removed from the exposed bone so that there is a stable edge of cartilage surrounding the defect. Multiple holes (also called microfractures) are then made in the exposed bone about 3 to 4 mm apart. Bone marrow cells and blood from the holes combine to form a “super clot” that completely covers the damaged area. This marrow-rich clot is the basis for the new tissue formation. The microfracture technique produces a rough bone surface to which the clot adheres more easily. This clot eventually matures into firm repair tissue that becomes smooth and durable.
The instruments currently used to make the microfractures are manual instruments such as curved picks and/or nitinol wires and guides. One powered option is a subchondral drill which is a straight drill covered by an outer sheath. The outer sheath covers the drill tip until it contacts bone and then the drill tip advances axially into the bone. The manual instruments are undesirable in that they typically require two hands to use since a mallet is used to drive the instruments into the bone. In addition, the impact loading of the mallet may cause the pick to slide or gouge the target site rather than puncture the site perpendicular to the axis of the trocar tip. The straight drill power instrument does not provide adequate accessibility or visibility to the site which is typically in a joint space.
An instrument that can form the microfractures quickly and at pre-determined angles with repeatability is needed. Also needed is an instrument that allows the surgeon to quickly place the microfractures in the desired position using only one instrument attached to power, and with improved accessibility and visibility to the site.